In a railway car, primary and secondary suspension systems are generally employed. The primary suspension system generally refers to the suspension between the journal bearing assembly and the truck frame. The journal bearing assembly carries a wheel-axle unit and acceleration forces generated by the wheel are directed to the primary suspension system with some of the forces being transmitted through the primary suspension system to the side frame. The secondary system refers to the system between a bolster on the truck and the car body and generally includes air or mechanical springs. The present invention is directed to primary suspension systems.
An example of primary suspension system may be found in a copending patent application entitled "Primary Suspension System for a Railway Car", Ser. No. 062,772 filed Aug. 1, 1979, now U.S. Pat. No. 4,278,029, assigned to the same assignee as the present invention.
There are presently in use railway cars in which the primary suspension system includes a rubber so-called shock ring fitted between a journal bearing assembly and side frame of a truck. The rubber ring used is compressed and clamped between the journal assembly and side frame. The compressed ring causes very high vertical and longitudinal stiffnesses in the order of about 100,000 pounds per inch.
Relatively high vertical stiffness in the primary suspension systems results in very little attenuation of the wheel accelerations to the truck frame. The relatively high longitudinal stiffness tends to maintain the axle position or wheel base within the truck frame.
Tests have indicated that reducing the vertical stiffness in the primary suspension systems reduces the accelerations in the truck frame. This tends to increase the useful life of the truck mounted equipment.
Tests have also indicated that reducing the longitudinal stiffness in the primary suspension system permits the axles on the truck to assume a more radial position with respect to the tracks when making turns. This reduces the angle of attack of the wheel flanges with respect to the tracks thereby reducing lateral wheel forces. The result is reduction of wheel and flange wear and longer life.